The man was arrested in early December and kept in custody after it emerged that six women, who he had sex with between 2006 and 2009, had been infected with the virus.
That figure has since risen to 29 after more women came forward to be tested, Il Messaggero reported. Ten previous sexual partners, however, tested negative for the virus.
Those infected were aged between 20 and 30, the newspaper said.
The man, called Valentino, faces charges of “grievous and incurable bodily harm” against the women, who he allegedly asked to forgo using a condom during sexual intercourse despite knowing he was HIV positive, prosecutors said.
He is alleged to have met some of the women through social networks such as Facebook and WhatsApp, occasionally proposing threesomes.
“The women were there, some responded straightaway...I didn't force anyone, they were up for it too,” he told Corriere in early December, adding that it was akin to a game of Russian roulette.
“Sometimes it goes wrong, but most often not. I lived with some of these women – we were in love, we had breakfast together in the morning, why should I have hurt them?”
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Some 3,695 people in Italy were diagnosed with HIV in 2014, a number which had seen little change over the three previous years.
Most of the new diagnoses were among 25 to 29-year-olds, who mostly became infected after not using a condom during sex, the report from Italy's higher institute of health (ISS) said.